Just the Bird Flu Facts, Ma’am

I’m seeing a ridiculous amount of misinformation going around about the bird flu outbreak, including every kind of conspiracy theory. Maybe I can clear up a few misconceptions and provide some accurate information.

Bird Flu has been around for years. Why are they killing chickens now when they didn’t before?

There are several different viruses that cause bird flu. For years, a class of bird flu called Low Pathogenic Avian Influenza (LPAI) has periodically circulated through domestic poultry flocks and among wild bird populations. LPAI usually doesn’t cause serious illness. Many birds can carry the virus without showing symptoms. Affected flocks commonly recover and continue producing eggs.

But what we’re dealing with now is different from the usual types of bird flu. It’s called H5N1 and was first identified in geese in China in 1996. In 1997, it was discovered in 18 people in Hong Kong, 6 of whom died. Then in 2020, a new variant of H5N1 was detected in wild birds in Europe. It reached wild birds in the U.S. and Canada in late 2021, and has spread to wild birds in all 50 states.

In February 2022, H5N1 was found in backyard and commercial poultry flocks in the U.S. It was causing serious illness and death in the infected chickens. In spite of all efforts to control it, it has continued to spread to new flocks.

Why do they kill the chickens? Why don’t they let it run it’s course so the hens can get back into production?

The new strain has mutated into deadly new types, such as the H5N1 Gs/GD lineage and H5N2/N8. These have a very high mortality rate in chickens and turkeys. Entire flocks can be dead in less than a week after being infected.

Infected flocks need to be euthanized as fast as possible to help slow down the spread to other farms. Also, the faster the premises can be sterilized, the faster the farm can repopulate and get back into business.

No farmer wants to see their entire flock culled, and it wouldn’t be done if it weren’t absolutely necessary. Farmers are compensated for culled birds, but this only partly covers their loss. The process is very expensive for the farmer, and puts his livelihood at risk.

The number one reason that makes it imperative that a flock be quickly killed is to minimize the possibility of a human pandemic. The HPAI Bird Flu has been rapidly mutating and has infected multiple species of mammals, including humans. So far, the number of human infections has remained low, but infectious disease experts fear that these strains could mutate further, allowing it to spread from person to person, which could result in another worldwide pandemic. The more humans become infected through contact with sick poultry, the more chances the virus has to mutate into a form that initiates a human pandemic. This must be prevented at all costs, and the best way to do this is to stop it from spreading to more poultry farms.

Is there a vaccine for bird flu?

A vaccine is in development, but it will be a while before it can be used. For one, many countries we export to do not allow poultry products from vaccinated birds. Another concern is, due to the high mutability rate, if birds vaccinated against one strain of bird flu come in contact with a different strain, there’s a real possibility that it will mutate into an even more deadly form.

Update added Mar 11 to clarify a point: Yes, I know bird flu vaccines already exist. Those vaccines are not effective against the new mutated strains.

Why are laying hens being killed but not broilers?

This requires a multi-fold answer.

Partly, it’s because broilers are primarily produced in the Southeast, which hasn’t seen much bird flu. The Midwest is where most egg farms are located and where the bird flu outbreak is intense.

Even if broiler farms start getting hit, the impact would be lower. Broilers are butchered around 6 weeks of age. That fast life cycle results in a shorter window of time in which they can be infected. And if a flock did get infected, the farmer will lose no more than a few weeks of production. He/she can disinfect the facilities, repopulate, and have birds ready to harvest in a very short amount of time.

Laying hens are a whole different story. It takes about 25 weeks to grow the chicks to egg laying age, and that 25 weeks is all cost with no return. If a laying flock is hit with the virus, the farmer is completely out of business for several months, while spending massive amounts of money on feed and other expenses involved in raising hundreds of thousands of chickens to laying age.

If it’s infecting wild birds, why aren’t there dead birds all over?

Songbirds, pigeons and doves are mostly resistant to bird flu. These are the birds you’ll see in your yard and in cities. Sometimes they will become infected but not show any symptoms. These carriers are capable of spreading it to susceptible species. Occasionally they actually will get sick and die from it, but the number of dead ones is small, and you’re not likely to notice.

Waterfowl and shorebirds are more susceptible to becoming infected, and often become carriers. Now and again it will hit a population or waterfowl or shorebirds hard enough to cause a lot of deaths, but this has not been seen in great numbers of populations.

Raptors (such as eagles, hawks and vultures), are very sensitive to bird flu. When they become infected, many die. Since this latest outbreak started in 2022, several hundred Bald and Golden Eagles have died from it.

Out of all bird species, chickens and turkeys are the most susceptible to it. When they get infected with one of the mutated HPAI strains, spread is extremely rapid and most birds in the flock die. This doesn’t just apply to domestic flocks; some wild turkey flocks have succumbed to it.

Commercial flocks are usually in enclosed buildings. How do they get infected?

Poultry farmers take many precautions to keep their flocks disease free, including forbidding workers from owning or coming into contact with birds. Poultry workers don’t always follow the rules. They can unknowingly carry the virus into the building on their clothing or shoes.

The virus can also find it’s way in via rodents, contaminated cages, trucks, feed, and many other ways.

Wild birds can also carry the virus without getting sick. Sometimes they’ll manage to find their way in through a loose corner of barn siding, or some other way.

Additional Information

Wild & Domestic Mammals:

Globally, sporadic HPAI A(H5N1) virus infections in mammals have been reported in more than 50 species across the continents of Asia, North America, South America, and Europe.

In Canada and the US, the mutated strains have been detected in cats, dogs, foxes, skunks, bobcats, fishers, bears and domestic alpacas.

Outside the U.S. avian flu has infected farmed mink. It has also caused losses at marine mammal colonies in South America, such as sea lions in Peru and Chile, and sea elephants in Argentina.

Europe and Asia have both found it in numerous species of wild mammals.

Farm Mammals:

Both pigs and dairy cows are becoming infected.

Epidemiologists are especially concerned about the pigs, because of the way that pigs can become infected with both bird and animal flu viruses. When a pig is exposed to both human and bird flu, their unique biology allows the two strains to swap genetic matter in a process called reassortment. The bird flu virus then has the ability to become a novel human strain, which can be transmitted from human to human, which results in a pandemic. The most recent such pandemic was the swine flu virus H1N1 outbreak in 2009. Currently only a tiny number of pigs have become infected.

Cattle are another concern. A multistate outbreak of HPAI A(H5N1) bird flu in dairy cows was first reported on March 25, 2024. This is the first time that these bird flu viruses had been found in cows. As of Feb 14, 2025 there have been 972 confirmed cases of bird flu in cattle in 17 states. Because of this growing outbreak, dairy herds are being tested regularly in hopes of slowing the spread.

The spread of the virus among cows is a sign that it could mutate in them, making it easier for it to spread to other animals or potentially humans. Bird flu is found in the milk and respiratory discharges of infected dairy cows. This is why health officials have been warning about drinking raw milk. Several human cases have occurred in people who had been exposed to infected dairy cows, which is alarming to the medical community, since it possibly indicates that the virus can jump from cattle to humans.

If the virus continues spreading through the cattle population, we could potentially be facing shortages of milk, products made from milk, and maybe even beef products.

Human Cases

So far, 68 people in the U.S. have tested positive for bird flu in 12 states since this current outbreak began in 2022. These cases are mostly believed to have been transmitted to the patients by animals.

However, several human-to-human transmissions of avian influenza viruses is thought to have occurred. This seems to have happened when there has been close or prolonged contact with an infected patient. No sustained human-to-human transmission has been identified, so we’re not in immediate danger of a pandemic.

Some highly pathogenic strains of avian influenza viruses, such as the Asian H5 and H7 lineages, are known to cause severe illness and death in humans, but the pathogenicity is unknown for many strains.

Update added Mar 11: Trials for a human vaccine are underway now. The medical community wants to be ready in case this new bird flu causes a pandemic in people.

Human Symptoms

Some people have been found to be infected with the virus, yet show no symptoms. Most people get sick, but the symptoms can range from mild to severe illness that requires hospitalization.

Reported symptoms can include:

• Conjunctivitis
• Cough
• Fatigue
• Fever
• Headaches
• Muscle or body aches
• Runny nose
• Shortness of breath

Try to Avoid It:
The CDC currently considers bird flu a low public health risk, but people still need to take steps to protect themselves. If you are in an area where bird flu has been identified:

1. Only consume pasteurized dairy products.
2. Thoroughly cook your eggs, meat and poultry.
3. Avoid contact with wild, sick or dead birds and livestock.
4. Don’t give your pets raw milk or raw pet food.
5. Keep pets away from sick or dead birds when they’re outside.
6. If you do come in contact with potentially infected animals or birds or their byproducts, wash your hands vigorously.
7. Pay attention to public health recommendations.